Electron tube



June 2, 1959 D. A. SOKOLOV 2,889,482

ELECTRON TUBE Filed Feb. 18. 1953 INVENTOR I 1 David A.SokoloV ATTORNEYELECTRON TUBE David A. Sokolov, Lynn, Mass, assignor to ColumbiaBroadcasting System, Inc., a corporation of New York, doing business asHytron Radio & Electronic Co., Danvers, Mass, a division of ColumbiaBroadcasting System, Inc.

Application February 18, 1953, Serial No. 337,530

2 Claims. (Cl. 313-278) This invention relates in general to electrontubes and in particular to rectifying types.

In those rectifier applications where power transformers are used, lowvoltage power rectifiers usually employ filimentary cathodes rather thanindirectly heated sleeve cathodes. Numerous reasons exist for thepractice, one of which is the cost factor, filamentary cathodes beingcheaper to construct than the heaters and sleeves of indirectly heatedcathodes. Also, since the rectifier output is to be filtered before use,no hum problem is encountered. Finally, no heater-cathode leakage orbreakdown need be considered and greater efficiency is achieved.

Quite often, the low voltage power rectifiers in question are of thefull Wave type. However, since the two sections are identical, thedescription hereinbelow will be of a single section. Each such sectionusually includes a flattened oval anode with a hairpin filament ribbonwithin the oval. The filament is arranged to be as widespread aspossible at the open end which is normally at the bottom for convenientattachment to stem leads. At the top the closed end is looped over amica support which is a part of the mica disk which supports and spacesStates Patent all of the tube elements from each other and from thebulb. The anode is usually constructed of nickel or nickel alloy whichis carbonized to aid in heat dissipation. The base metal is a relativelypoor conductor of heat and those areas on the oval which are closest tothe filament actually reach red heat from the electron bombardment whenthe tube is run at peak ratings. The emission current density in theareas of peak emission current flow between the filament and the closestportions of the anode becomes so great that the voltage required on theanode for proper operation also becomes undesirably high.

- Another problem associated with the conventional design in filamentarytype rectifiers is sagging and general structural weakness of thefilament which is a relatively flexible ribbon. This problem isaccentuated by expansion due to the high temperature at which thefilament is run. It is sometimes desirable to mount the rectifier inpositions other than vertical where sagging can cause portions of thefilament to approach the anode creating further maldistribution ofheating or, in the worst case, shorting of the filament to the anode andtube failure.

Therefore, it is an object of the present invention to provide arectifier having permanent geometric relationships between elements.

It is a further object to provide a rectifier having a non-saggingfilament.

It is a still further object to provide a vacuum tube filament and anodewhich are matched for more efiicient use of anode surfaces.

It is still another object to provide a vacuum tube anode havingsymmetry about a filament.

It is another object to provide a rectifier having low voltage dropacross its elements.

. 12 as well as to give In general, the present invention consists in adouble section rectifier tube each section of which includes afilamentary cathode and an anode which are matched in structure forefiiciency of material utilization. The anode has a contour which placesa maximum surface area equidistant from the filament. The filamentitself is supported in such a manner that the conditions of optimumgeometry are maintained at all times despite expansion or sagging of thefilament. This permits mounting of the tube in any position, lowers thetube drop and generally improves tube operation. For a betterunderstanding of the invention, together with other and further objects,features, and advantages, reference should be made to the followingdescription which is to be read in connection with the accompanyingdrawings in which:

Fig. 1 is an elevation view, partly cut away, of a double dioderectifier embodying principles of the present invention;

Fig. 1A is a cross-sectional view of the rectifying tube shown in Fig. 1taken along the plane of line 1A1A. Fig. '2 is an enlarged top view,partly cut away, of the mica support and associated components utilizedin the diode rectifier of Fig. 1; and

Fig. 3 is a view of a section of Fig. 2 along line 3-3.

Referring now particularly to Fig. l, and Fig. 1A, there is disclosed aglass envelope 12 which is attached in conventional fashion to a base13. Within the envelope are similar anodes 14 and 15. Anode 14 which isvisible in considerable detail in this view is formed of two similarcarbonized nickel stampings, each stamping having a pair ofsemi-cylindrical channels out along its length. These channels at oneend of the stamping approach the longitudinal axis of the stamping anddiverge symmetrically from the axis along its length. Each side of thestamping is turned through along its length, and two of the stampingsare welded together to form each anode. The anodes 14 and 15 thus have asubstantially T-shaped cross-section, the diverging c'hannels matching,however, to form two diverging cylinders through the length of eachanode.

As is conventional in vacuum tube practice, a top mica 16 is used toretain the anode and other tube elements in spaced relationship fromeach other and from bulbstructural rigidity to the whole device. Topmica 16 is provided with additional openings for purposes explainedbelow. Mounted on top mica 16 are getter support rods 17 and 18. Rods 17and 18 are actually formed from a single wire loop welded to a plate 19disposed beneath top mica 16. The ends of the loop then are bent to passupwardly through openings in top mica 16.

Also passing through openings in top mica 16 are filaments for each ofthe anodes. Filaments 20 and 21 are welded at their lower ends to stemleads of the tube and pass upwardly centrally of the diverging cylindersof anodes 14 and 15,-through openings in top mica 16 and are returned tothe stem through other openings in top mica 16 and through the othercylinders of their respective anodes. A spring mica 22 and double coiledsprings 23 and 24 are also provided as may be better seen and explainedby reference to other figures of the drawing.

Referring now to Figs. 2 and 3 of the drawing, spring mica 22 isprovided with openings to accommodate filaments 20 and 21, and gettersupport rods 17 and 18. Between the openings for filament 20, a bridgeof mica is formed to support filament 20. Similar support is affordedfilament 21. Openings are also provided in top mica 16 for filaments 20and 21, getter support rods 17 taken through a portion and 18, and anodetabs 25 and 26. The openings in both top mica 16 and spring mica 22 forgetter support rods 17 and 18 are only slightly larger than the rodsthemselves. Double coiled springs 23 and 24 are compressed between topmica 16 and spring mica 22, the internal diameter of the smaller coil ofeach of springs 23 and 24 being of a size to fit getter support rods 17and 18 fairly closely, the springs being free to move, however. Theexternal diameter of the smaller coils is smaller than the internaldiameter of the larger coils which permits the smaller coils to nestwithin the larger when the mount is assembled on the stem of the tube.In other words, when the tube is assembled the ends of filaments 20 and21 are threaded through spring mica 22 and top mica 16 and are passedthrough the proper cylinders of anodes 14 and 15. At the stem, thefilaments are pulled taut bending spring mica 22 slightly as shown inFig. 3 and compressing springs 23 and 24. Thus, any expansion offilaments 20 and 21 is compensated for by springs 23 and 24 which willexpand to force spring mica 22 away from top mica 16 and stretchfilaments 20 and 21 taut to maintain them centrally disposed withintheir respective anode cylinders. The location of the return loops offilaments 20 and 21 on spring mica 22 is such that a balanced springingaction is had. The filaments are maintained centrally of the anodecylinders despite orientation of the tube.

The diverging design of the cylinders of anodes 14 and 15 permits a morenatural positioning of hairpinshaped filaments 2t and 21 and, moreimportant, brings more of the anode surfaces into play in dissipatingheat. As was mentioned, previously, the carbonized nickel alloy of whichthe anodes are made is a relatively poor heat conductor, and carryingthe cylinders outwardly to the edges of the anodes aids in distributingthe heat over more anode surface for easiler dissipation.

The walls of the anode cylinders being equidistant from the filamentsabout their entire 360 provides so much more anode area being bombardedby electron emission that the anode runs much cooler than theconventional flattened oval. anode. Also, the provision of greateruseful anode area decreases the emission current density, the currentpaths no longer being confined to segments as in the flattened oval butflowing in complete circular planes about the filaments to the anodecylinders. The resulting decrease in current density gives less tubevoltage drop and a voltage output which is higher than that derived fromthe prior art design in similar circuit applications.

This invention should be limited only by the spirit and scope of theappended claims.

What is claimed is:

l. A rectifier tube comprising, a hairpin-shaped filament attached atits open end to leads of said tube, an anode having cylindrical Walls,said cylindrical walls being symmetrically disposed about the straightlegs of said hairpin-shaped filament, a mica disk having a pair ofopenings receiving said filament, and spring means resiliently urgingthe portion of said mica disk between said openings against the closedend of said filament to maintain said filament under tension andcentrally disposed in said cylindrical walls.

2. A rectifier tube comprising, an evacuated envelope having leadsextending through the lower end thereof, a pair of anodes of rectangularconfiguration each being disposed with its longitudinal axis parallel tothat of said envelope, said anodes being supported by said leads at saidlower end, a first mica disk supporting said anodes at the upper end ofsaid envelope, a metal plate attached to the under side of said firstmica disk, a pair of upwardly extending getter support rods passingthrough said first mica disk and Welded to said metal plate, a secondmica disk disposed parallel to and above said first mica disk, saidgetter support rods also passing through said second mica disk, a coiledspring wrapped on each of said getter support rods between said firstand said second mica disks, eachof said anodes having two cylindricalwalls running longitudinally thereof, the axes of said cylindrical Wallslying on either side of the longitudinal axis of their respective anodesand diverging symmetrically therefrom toward the lower end of saidanodes, a hairpin-shaped fine ribbon filament threaded centrally throughsaid cylindrical chambers of each of said anodes and welded at its endsto two of said leads at said lower end, said filaments passing throughspaced openings in said first and saidsecond mica disks, the closed loopof said hairpin-shaped filament passing over the upper surface of saidsecond mica disk, the ends of said filament being welded to said leads,the length of said filaments being suificient to compress said springs,whereby said second mica disk maintains tension in said filaments andretains them centrally in said cylindrical walls.

References Cited in the file of this patent UNITED STATES PATENTS1,522,286 Clausen Jan. 6, 1925 1,558,111 Metcalf Oct. 20, 1925 1,597,893Huppert Aug. 31, 1926 1,605,735 Hough Nov. 2, 1926 1,657,221 Metcalf etal. Ian. 24, 1928 1,689,971 Robinson Oct. 30, 1928 1,720,442 RobinsonJuly 9, 1929 1,905,872 Houck Apr. 25, 1933 1,999,300 Lyle Apr. 30, 19352,075,611 Hoffman Mar. 30, 1937

